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Date Calculator

Days between dates, add or subtract days, business-day count.

Runs in your browser

Pick a mode. Either two dates - we show the gap in days, weeks, months, years and business days - or one date plus an offset, returning the resulting date and weekday.

Days

0

Weeks

0.00

Months

0

Years

0

Business days

0

How to use it

  1. Pick a mode

    Difference between two dates, or add/subtract days from a base date.

  2. Enter the dates

    ISO-8601 (YYYY-MM-DD). Today is pre-filled.

  3. Read the result

    Days/weeks/months/years + business days for diff; resulting date + weekday for add.

What is it?

A date calculator handles two everyday questions: 'how many days between X and Y?' and 'what's the date N days from now?'. Calendar arithmetic looks simple but breaks for month boundaries and leap years; using ISO-8601 rules avoids the surprises.

When to use it

Project deadlines, invoice ageing, contract renewal dates, gestational dates, sprint countdowns, anniversaries, weekday lookup for past events ('what day was 14 March 1987?').

Common mistakes

Treating months as 30 days each - they aren't. Counting business days without subtracting public holidays. Mixing UTC and local time when crossing midnight - the calculator uses UTC to stay stable across timezones.

FAQ

How are business days counted?
Saturdays and Sundays are excluded. Public holidays are not - we don't know your jurisdiction. Subtract national holidays manually if needed.

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